1. Field of the Invention
This invention relates to a database restructuring apparatus for restructuring a database, and a computer-readable recording medium recording a database restructuring program, and more particularly to a database restructuring apparatus configured to reduce online service interruption time, and a computer-readable recording medium recording a database restructuring program.
2. Description of the Related Art
When the capacity of a database becomes insufficient, the database is restructured. However, in order to physically restructure the database, it is required to temporarily save data from the database and then store the data in the database again. Therefore, if the database is a large-scale one, it takes a long time to save and store the data again. For this reason, it is difficult to restructure database while providing online services for which a response within a predetermined time period is required to be always ensured.
In general, physical restructuring of a database during online operation is given up, and instead, the operation of expanding the database is executed in an online service interruption time period e.g. on weekends. In this case, however, if there occur more online jobs than expected, the capacity of the database can become insufficient during execution of online operation. If the capacity of the database runs short during online operation, it is impossible thereafter to continue online transactions, which causes a great deal of inconvenience to users.
To cope with this problem, a method is generally employed in which a margin is given to the storage capacity of a database so as to prevent the capacity of the database from becoming insufficient before weekends. In this case, however, the database has to secure a larger storage capacity than necessary, which causes degradation of utilization efficiency of resources.
There have also been proposed various techniques for restructuring a database while minimizing service interruption time (see e.g. Japanese Unexamined Patent Publication Nos. 06-75840, 10-207754, and 2003-6020).
However, in the inventions disclosed in Japanese Unexamined Patent Publication Nos. 06-75840, 10-207754, and 2003-6020, it is required to store an update log associated with services provided during database restructuring, and reflect the update log in the restructured database. For this reason, a service is inevitably interrupted during execution of processing for reflecting the update log in the database. Further, as the database is larger, it takes longer to migrate data, and the data amount of update logs becomes large. As a result, time required for reflecting the update logs in the restructured database increases, which prolongs a service interruption time period.
It should be noted that the present assignee has proposed in Japanese Patent Application No. 2004-132350, a database restructuring method which is capable of restructuring a database without interrupting services. However, this invention targets only an index-based database, and because not every database is managed by the index-based method, the applicability of the invention is limited.